Soaring fuel prices, shrinking water resources, and increased regulation of wastewater treatment plant effluent are forcing wastewater treatment plant operators to manage their key units more efficiently.
Typically, key units or components of a wastewater treatment plant include a anaerobic digester (AD) and membrane bioreactor (MBR). The AD and MBR operate in a coordinated and an interdependent fashion, hence any upsets or variations in any key unit affect functionality and performance of the rest of the key units. The wastewater feed to the AD, for example, may have significant variations in flow rates, influent chemical oxygen demand (COD), total suspended solids, total soluble COD, temperature, nitrogen, phosphates, sulfates, and pH. The variations in the AD, in turn, impact operations of downstream process units, such as the MBR.
Conventionally, the variations in the key units are monitored periodic manual sampling and off-line laboratory tests to monitor the system performance, identify any abnormal condition due to variations in the wastewater feed, and decide on appropriate remedial action. Unfortunately, these lab tests are time consuming and infrequent manual sampling are not sufficient to detect potentially adverse changes in a timely manner. Also, manual operation is often inadequate in taking timely corrective actions needed to mitigate effects of variations and avoid any upsets. In particular, upsets in the AD can lead to instabilities which, if undetected or not corrected in a timely manner, can eventually cause a washout condition with loss of active biomass requiring costly shutdown and re-seeding. Also, whenever AD performance is hindered, biogas generation is sacrificed and the load on downstream MBR can become overwhelmingly high leading to violations in MBR effluent water quality.
These factors often lead to over-design and very conservative operation of the AD and MBR to avoid any potential upsets that can destabilize the AD and MBR. However, a conservative operation often means inefficient operation involving overdosing chemical additives and over-aerating to allow for unknown process variations, and thus unnecessary high operating costs.
Thus, a need exists for an improved method of operating a wastewater treatment plant through monitoring and controlling the AD and MBR of a wastewater treatment plant.